Experience of using commercial rotary machine to p

2022-08-13
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Experience of printing offset paper with commercial rotary machine

commercial rotary machine is mostly used for printing high-end products, such as printing periodicals, magazines and various commercial advertisements with light coated paper and coated paper, but it is not suitable for printing offset paper. However, due to the increasing number of color pictures and texts in students' textbooks, using the traditional rotary printing machine without drying device is often prone to quality problems such as dirt, ink instability and so on. Although it can be solved by reducing the amount of ink, the products printed in this way are often dark in color and poor in level expression. Therefore, the commercial rotary machine with drying device can be used for printing, which can eliminate the quality problems such as dirt, and the ink color is bright, and the picture level is rich. However, when printing offset paper with commercial rotary machine, the following problems should be paid attention to

1. Reduce the tension of paper tape

the tension of paper tape plays a decisive role in the overprint of rotary machine. Its setting principle is: on the basis of ensuring the accuracy of overprint and the continuous development of China's economy and society, the smaller the tension of paper tape, the better. Compared with coated paper, offset paper has poor toughness, brittleness and is easy to fracture. In view of this situation, it is necessary to try to gradually reduce the tension after starting the machine on the premise of ensuring the accuracy of overprint. Our experience is that for the same quantitative light coated paper and offset paper, the tension of the former is generally more than twice that of the latter. Adjusting the tension in this proportion can basically ensure that there is no paper in printing, and the overprint is accurate and stable

2. Reduce the printing machine speed

the faster the printing machine speed is, the higher the requirements for paper tensile force are. For light coated paper, the printing machine can run at a speed of 40000 prints/hour without paper breaking; For offset paper, the printing machine speed is generally 32000 prints/hour, sometimes it can only reach 28000 prints/hour. In production, when printing offset paper, paper breakage often occurs when the paper roll is small, especially when storing paper. The machine speed displayed on the paper rack display is not consistent with the machine speed of the host machine. For example, the machine speed before paper storage is 25000 prints/hour, while the machine speed displayed at the paper rack during paper storage is 30000 prints/hour. That is to say, when storing paper, the machine speed of the host machine is increased by 20%, and the paper tape is naturally easy to break. Therefore, when storing paper in the paper roll, the machine speed should be reduced by 1/5 in advance to prevent paper breakage

3. Stop the machine to automatically clean the rubber blanket

when printing light coated paper, the automatic cleaning of the rubber blanket without stopping the machine can improve the work efficiency, but it cannot be done when printing offset paper. Because the offset paper is brittle, there are many paper wool and paper powder, it is difficult to wash the blanket when it is piled up, and the paper is easy to break when it is cleaned without stopping the machine, so the automatic cleaning of the blanket when stopping the machine is often used, which can not only ensure the continuous paper, but also thoroughly clean the blanket every time

4. Reduce the oven temperature appropriately

the oven can heat the printed matter to dry quickly, and the higher the temperature, the better the drying effect. Offset paper has good ink absorption performance. Setting all these may lead to printing problems. The oven temperature can be reduced appropriately, but it depends on whether the printed matter can be dried thoroughly and whether there is rubbing and dragging. Generally, the oven temperature is 15 ~ rdquo lower than that when using light coated paper; Tang chuanrudder, general manager of Guochuan electronics, said 20. C is enough

5. The concentration ratio of silicone oil should be appropriately lower

the function of coating silicone oil is to prevent rubbing, dragging and static electricity. Due to the rough surface of offset paper, the ink absorption performance is much higher than that of light coated paper, so the proportion of silicone oil should be appropriately lower, which is generally half of the proportion concentration of printing light coated paper

6. The concentration ratio of fountain solution is slightly higher

offset paper has more paper powder, which will be continuously transferred to fountain solution during the printing process. As the paper powder is alkaline, which reduces the acidity of the fountain solution and makes the printing easy to get dirty, the proportion concentration of the fountain solution should be slightly higher, and the water supply should be slightly larger

7. Regularly clean the water tank and bucket

there is a lot of paper powder in the offset paper. The paper powder is continuously transferred to the bucket and water tank through the water roller, and will constantly wear the printing plate, reduce the printing resistance of the printing plate, and block the filtration in the water tank and bucket. Therefore, the water tank and bucket should be cleaned once a week, and the dirt such as paper powder should be cleaned to eliminate the harm of paper powder

8. Car washing should be carried out once a shift

when printing offset paper, there will be a lot of paper powder in the ink roller and water roller, which will not only wear the ink roller and water roller, affect the ink transmission, but also wear the printing plate and accelerate the aging of the ink roller and water roller. The hydraulic testing machine has a high power to weight ratio. Therefore, the ink roller and water roller should be cleaned every shift, and the paper powder should be cleaned. When cleaning, use car washing water first, and then clean with clean water

9. Ingenious application of two sides of paper

when printing, it is inevitable to encounter the situation that there are large areas of pictures and texts on one side and few pictures and texts on the other side. When the hair loss on the side with a large area of graphics and texts is extremely serious, we have used methods such as reducing the amount of ink, water, adding additives, changing the ink, changing the printing color sequence, and so on, but they have not been solved. Finally, we try to change the paper roll to another side and print a large area of graphics and texts with a relatively smooth side, and the effect is very good

10. Secondary utilization of printing plates

sometimes due to the requirements of printing cycle, the product cannot be printed at one time, but it is a pity to discard the printing plates that can still be used. We use the method of manual unloading, so that the printing plate can be reused. However, the bent and deformed printing plate must be leveled when installing the plate, so that it can be used normally

information source: Printing Technology

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